Recycling treatment method of seawater diatom culture solution

Abstract

The invention provides a reutilization treatment method of a seawater diatom culture solution. The reutilization treatment method comprises the following steps: S1, sequentially performing flocculation and primary filtration on a seawater diatom culture solution which is subjected to seawater diatom culture and harvest treatment, so as to obtain a first filtrate; s2, sequentially carrying out macromolecular substance degradation and separation treatment on the first filtrate to obtain a recycled culture solution; and S3, mixing the reutilized culture solution with the seawater diatom species, and culturing new seawater diatom. The reutilization treatment method disclosed by the invention can be suitable for cyclic utilization of the culture solution in a large-scale seawater diatom culture process, and plays an important role in improving economic benefits and ecological benefits of diatom culture.

Description

Technical Field

[0001] The present invention relates to the technical field of algal culture, and in particular, to a method for recycling and treating seawater diatom culture solution. Background Art

[0002] Diatoms are widely distributed in the ocean and are a single-celled planktonic ecological group in seawater diatoms (seawater diatoms are a type of microalgae widely distributed in the marine environment and belong to the phylum Diatomophycota). They are the main group of marine phytoplankton, with both the quantity and variety accounting for more than 90%. Diatoms have particularly high nutritional value, being rich in nutritional components such as fucoxanthin (FX) and eicosapentaenoic acid (EPA) that are edible and medicinal. Moreover, they have characteristics such as a fast growth rate and a short cycle, and have high market value. Diatoms such as Odontella aurita and Phaeodactylum tricornutum have been included in the new resource food catalog in some European and American countries.

[0003] Currently, domestic research on seawater diatoms producing fucoxanthin and EPA still remains at the laboratory stage, and large-scale production is difficult to achieve. One of the reasons is that the salinity in the culture solution of seawater diatoms needs to simulate seawater salinity; otherwise, the cells will dehydrate or rupture. Therefore, the high-salinity culture solution after harvesting cannot be directly discharged into the environment and needs water purification, which will generate a large amount of breeding costs. For every 1 ton of dry algae produced, nearly 1000 tons of high-salinity culture solution will be generated. And this high-salinity culture solution cannot be directly discharged into the environment and must be treated to meet the discharge standards before it can be discharged, and it also limits the regionality of seawater diatom production. Moreover, existing research has found that the substances present in the seawater diatom culture solution after harvesting (i.e., after collecting most of the algal cells in the culture solution) are mostly extracellular products, which are metabolites of seawater diatoms (which may have an inhibitory effect on cell growth and thus need to be removed), and the types of these substances are difficult to clearly distinguish, further causing certain obstacles to the removal and recycling of culture solution impurities.

[0004] Currently, only some existing technologies have disclosed solutions for the recycling of microalgae culture solutions. Microalgae are the general term for various small algal microorganisms including diatoms, but seawater diatoms are not mentioned in these solutions. For example:

[0005] Patent application document CN108865893A discloses a method for harvesting and recycling Dunaliella salina (a seawater green alga belonging to the Chlorophyta phylum and also a seawater alga growing in a high-salt environment (salt tolerance of 30 - 35%)) by alkali flocculation. Specifically, it discloses culturing microalgae using bicarbonate in a microalgae culture system, and using the highly alkaline environment generated by the culture medium after culturing microalgae, adding low-concentration Ca 2+ 、Fe 3+Flocculating ions react with carbonate or hydroxide ions to promote the sedimentation of microalgae, thereby reducing the cost of microalgae harvesting. After that, the high-alkaline environment in the supernatant is used to absorb CO2 to generate bicarbonate, which provides a carbon source for microalgae growth, thus reducing the carbon supply cost. In addition to carbon, a part of nitrogen, phosphorus, and trace elements is also lost during the cultivation process. During the flocculation sedimentation process, part of Ca 2+ , Mg 2+ , Fe 3+ , etc. will be lost. Therefore, for cyclic cultivation, these nutrient elements and ions need to be replenished to their concentrations in the initial culture medium. After that, physical or chemical methods are used to remove the inhibitors in the recycled culture solution to ensure the realization of cyclic cultivation.

[0006] The key lies in solving the problems of high bicarbonate cost when using bicarbonate as a carbon source for microalgae cultivation and high cost of harvesting microalgae by flocculation method. When it comes to the reuse of the culture solution after microalgae harvesting, only physical or chemical methods for treating the recycled culture medium are mentioned. In its examples, the effects of treating 50% of the culture medium taken out after 3 days of cultivation (at this growth stage, a large amount of metabolites inhibiting algae growth have not been produced) by using filter membrane, activated carbon, and NaClO alone are investigated respectively. However, this part of the taken-out culture medium is not the culture solution after microalgae cultivation and harvesting, and there are at least differences in composition between them (such as metabolites that may inhibit cell growth). In addition, all the cultivations in these examples are carried out in 1L conical flasks.

[0007] Patent application document CN109721197A discloses a device and its using method for treating and recycling microalgae culture water, and specifically discloses a using method of a device for treating and recycling microalgae culture water. The specific process includes pumping the cultivated microalgae and culture solution in the photobioreactor into the algae separation system, pumping the separated culture wastewater into the sedimentation tank for sedimentation, discharging pollutants and impurities, pumping the well-sedimented wastewater into the collection pool, pumping the wastewater in the collection pool into the protein separator for decontamination treatment, using an ozone generator to generate ozone and introducing it into the protein separator, and using an ultraviolet sterilizer to sterilize the wastewater in the collection pool. The treated finished water is pumped back into the photobioreactor as microalgae culture water. The key lies in providing a continuous device, without mentioning the type of microalgae, nor investigating the effect of recycling and cultivating microalgae after treating the culture water.

[0008] The patent application document CN112408645A discloses a method for recycling microalgae culture wastewater, which specifically includes centrifugal filtration, multi-layer sieve filtration, aeration tank treatment, and vacuum filtration of the microalgae culture wastewater to achieve the purpose of recycling the microalgae culture wastewater. The disclosed solution is only a solution for filtering and treating the microalgae culture solution, and the application object mentioned therein is Spirulina (a microalgae organism belonging to the Cyanophyta).

[0009] Therefore, in order to promote the large-scale cultivation of marine diatoms, it is urgent to find a method that can efficiently and low-costly treat the marine diatom culture solution. Summary of the Invention

[0010] The main object of the present invention is to provide a method for treating and recycling a marine diatom culture solution to improve the problem of difficult treatment and discharge of the marine diatom culture solution in the prior art.

[0011] To achieve the above object, according to the first aspect of the present invention, a method for treating and recycling a marine diatom culture solution is provided. The method for treating and recycling includes: S1, subjecting the marine diatom culture solution after the nth marine diatom culture and harvesting treatment to flocculation and primary filtration in sequence to obtain a first filtrate; S2, subjecting the first filtrate to macromolecule degradation and separation treatment in sequence to obtain a recycled culture solution; S3, using the recycled culture solution to perform the (n + 1)th marine diatom culture on the marine diatom strain; n is a natural number greater than or equal to 1.

[0012] Further, the method for treating and recycling further includes: S4, repeating steps S1 - S3 for the marine diatom culture solution after the (n + 1)th marine diatom culture and harvesting treatment; preferably, the macromolecules include proteins, polysaccharides, and lipids.

[0013] Further, in step S2, after separating the products obtained by degrading the macromolecules and before obtaining the recycled culture solution, the method for treating and recycling further includes filtration treatment; preferably, the filtration treatment includes first filtration and / or second filtration. The first filtration is performed using the following filters: PP cotton filter and / or backwashing filter; the second filtration is performed using the following filter media: at least one of activated carbon, hollow fiber membrane, and ceramic membrane; preferably, the pore size of the PP cotton filter is 0.1 - 0.2 μm; preferably, the particle size of the activated carbon is 10 - 20 mesh, and the iodine adsorption value is 1100 - 1300 mg / g.

[0014] Further, flocculation includes: adding a flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment, and stirring; the flocculant is selected from at least one of polyacrylamide, chitosan, ferric trichloride, polyaluminum chloride, and polyferric sulfate; preferably, flocculation includes: adding a first flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment, and performing a first stirring to obtain a first stirred product; adding a second flocculant to the first stirred product and performing a second stirring to obtain a second stirred product; preferably, the first flocculant is selected from at least one of polyacrylamide and chitosan; the second flocculant is selected from at least one of ferric trichloride, polyaluminum chloride, and polyferric sulfate.

[0015] Further, the speed of the first stirring is 60 - 90 rpm; preferably, the speed of the second stirring is 60 - 90 rpm; preferably, the final concentration of the first flocculant is 1 - 5 ppm; preferably, the final concentration of the second flocculant is 5 - 15 ppm.

[0016] Further, primary filtration includes: introducing the culture solution to be primarily filtered into a double - layer micro - filter screen for primary filtration; wherein, the double - layer micro - filter screen includes a first micro - filter screen and a second micro - filter screen, and the pore size of the first micro - filter screen through which the solution first flows is larger than that of the second micro - filter screen through which the solution then flows; preferably, the pore size of the first micro - filter screen is 1 - 5 μm; preferably, the pore size of the second micro - filter screen is 0.2 - 0.5 μm; preferably, the introduction flow rate of the culture solution to be primarily filtered is 30 - 45 m 3 / h.

[0017] Further, macromolecular substance degradation includes: adding a disinfectant to the first filtrate and performing a fourth stirring; preferably, the disinfectant is sodium hypochlorite and / or chlorine dioxide; preferably, the time of the fourth stirring is 30 - 45 min; preferably, the chlorine concentration in the culture solution after macromolecular substance degradation is 10 - 20 ppm.

[0018] Further, separation treatment is carried out in a protein separator, and the treatment flow rate of the protein separator is 15 - 25 m 3 / h; preferably, the flow rate for the first filtration is 30 - 45 m 3 / h.

[0019] Further, S3 includes: disinfecting the recycled culture solution to obtain a pretreatment solution, mixing the pretreatment solution with the seawater diatom seed, and performing the (n + 1)th seawater diatom culture; preferably, the chlorine concentration in the pretreated solution after disinfection is 6 - 10 ppm.

[0020] Further, S3 includes: adding a seawater diatom medium to a mixture of the reused culture solution and seawater diatom seeds, and performing the (n + 1)-th seawater diatom culture; preferably, the volume ratio of the reused culture solution to the seawater diatom medium for mixing is (100 - 1000):1; preferably, the volume ratio of the reused culture solution to the seawater diatom seeds is (3 - 10):1.

[0021] Further, after the pretreatment solution is mixed with the seawater diatom seeds and before the (n + 1)-th seawater diatom culture, S3 further includes: adding a seawater diatom medium to the mixture of the pretreatment solution and the seawater diatom seeds, and then performing the (n + 1)-th seawater diatom culture; preferably, the volume ratio of the pretreatment solution to the seawater diatom medium is (100 - 1000):1; preferably, the volume ratio of the pretreatment solution to the seawater diatom seeds is (3 - 10):1.

[0022] Further, the seawater diatom medium contains nitrogen element, phosphorus element, iron element, magnesium element, zinc element, silicon element, vitamin B1, biotin, and vitamin B 12 ; preferably, the seawater diatom medium includes: 0.5 - 1.5 g / L NaNO3, 0.01 - 0.0315 g / L FeCl3·6H2O, 0.5×10 -4 -1.781×10 -4 . g / L MnCl2·4H2O, 0.5×10 -5 -2.3×10 -5 g / L ZnSO4·4H2O, 0.1×10 -5 -1.19×10 -5 . g / L CoCl2·6H2O, 0.5×10 -6 -2.5×10 -6 g / L CuSO4·5H2O, 0.2×10 -6 -1.84×10 -6 . g / LNa3VO4, 0.1 - 0.3 g / L NaSiO3·4H2O, 0.01 - 0.03 g / L NaH2PO4·H2O, 0.5×10 -4 -2×10 -4 μg / L vitamin B1, 0.1×10 -6 -1×10 -6 μg / L biotin, 0.1×10 -6 -1×10 -6 μg / L vitamin B 12 .

[0023] Further, the reuse treatment method further includes: when n > 5, evaporating and crystallizing the reused culture solution to obtain distilled water and crystal salts.

[0024] Applying the technical solution of the present invention, through flocculation, primary filtration, macromolecular substance degradation and separation and removal treatment of the harvested seawater diatom culture solution, substances that inhibit subsequent culture can be effectively removed, realizing the reuse of the culture solution, reducing the waste liquid discharge of seawater diatom culture by more than 80%, having a significant positive impact on environmental protection, and reducing the culture cost. In addition, the reuse culture method of this application is simple to operate and has high treatment efficiency, and is applicable to the recycling of the culture solution in the large-scale seawater diatom culture process, which plays an important role in improving the economic and ecological benefits of diatom culture. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It shows a schematic flow chart of the reuse treatment of the seawater diatom culture solution of this application;

[0027] Figure 2 It shows a curve graph of the dry weight of Odontella aurita changing with the culture time during a new round of culture in Examples 1, 2, and 3 of this application;

[0028] Figure 3 It shows a curve graph of the fucoxanthin content in Odontella aurita changing with the culture time during a new round of culture in Examples 1, 2, and 3 of this application;

[0029] Figure 4 It shows a curve graph of the dry weight of Odontella aurita changing with the culture time during a new round of culture in the control group of this application and Comparative Examples 1-2;

[0030] Figure 5 It shows a curve graph of the fucoxanthin content in Odontella aurita changing with the culture time during a new round of culture in the control group of this application and Comparative Examples 1-2;

[0031] Figure 6 It shows a curve graph of the dry weight of Odontella aurita changing with the culture time during a new round of culture in the control group of this application and Examples 1 and 4;

[0032] Figure 7 It shows a curve graph of the fucoxanthin content in Odontella aurita changing with the culture time during a new round of culture in the control group of this application and Examples 1 and 4;

[0033] Figure 8The graph showing the change in the dry weight of Odontella aurita over the culture time during a new round of culture for the control group, Example 4 and Comparative Example 3 of the present application is shown;

[0034] Figure 9 The graph showing the change in the fucoxanthin content in Odontella aurita over the culture time during a new round of culture for the control group, Example 4 and Comparative Example 3 of the present application is shown;

[0035] Figure 10 The graph showing the change in the dry weight of Phaeodactylum tricornutum over the culture time during a new round of culture for the control group and Example 5 of the present application is shown;

[0036] Figure 11 The graph showing the change in the fucoxanthin content in Phaeodactylum tricornutum over the culture time during a new round of culture for the control group and Example 5 of the present application is shown;

[0037] Figure 12 The graph showing the change in the dry weight of Odontella aurita over the culture time during a new round of culture for Example 1 and Comparative Example 4 of the present application is shown;

[0038] Figure 13 The graph showing the change in the fucoxanthin content in Odontella aurita over the culture time during a new round of culture for Example 1 and Comparative Example 4 of the present application is shown;

[0039] Figure 14 The graph showing the change in the dry weight of Odontella aurita over the culture time during a new round of culture for Example 1 and Comparative Example 5 of the present application is shown;

[0040] Figure 15 The graph showing the change in the fucoxanthin content in Odontella aurita over the culture time during a new round of culture for Example 1 and Comparative Example 5 of the present application is shown;

[0041] Figure 16 The graph showing the change in the dry weight of Odontella aurita over the culture time during a new round of culture for Example 1, Example 6 and Example 7 of the present application is shown;

[0042] Figure 17 The graph showing the change in the fucoxanthin content in Odontella aurita over the culture time during a new round of culture for Example 1, Example 6 and Example 7 of the present application is shown;

[0043] Figure 18 The graph showing the change in the dry weight and fucoxanthin content of Odontella aurita over the culture time during 1 - 3 new rounds of culture in Example 8 of the present application is shown;

[0044] Figure 19The graph shows the changes in the dry weight and fucoxanthin content of Odontella aurita with the culture time during the 4 - 6th new round of culture in Example 8 of the present application. Detailed implementation manners

[0045] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0046] Explanation of terms:

[0047] Fucoxanthin (FX): Also known as fucoxanthol, fucoxanthin, it is a natural pigment in the xanthophyll class of carotenoids, accounting for more than 10% of the total amount of approximately 700 naturally occurring carotenoids, with a color ranging from light yellow to brown. It is widely present in various algae, marine phytoplankton, aquatic shellfish and other animals and plants. It has anti - tumor, anti - inflammatory, antioxidant, weight - loss, nerve cell protection effects, and can increase the content of ARA (arachidonic acid) and DHA (docosahexaenoic acid) in mice. It has been widely used in the market as drugs, skin care and beauty products, and health products.

[0048] Eicosapentaenoic acid (EPA): Belonging to the ω - 3 series of polyunsaturated fatty acids, it is an essential nutrient for the human body. EPA can help reduce the content of cholesterol and triglycerides, promote the metabolism of saturated fatty acids in the body, thereby reducing blood viscosity, improving blood circulation, increasing tissue oxygen supply and eliminating fatigue. It can prevent the deposition of fat on the blood vessel wall, prevent the formation and development of atherosclerosis, and prevent cardiovascular diseases such as cerebral thrombosis, cerebral hemorrhage, and hypertension.

[0049] As mentioned in the background art, when culturing marine diatoms in the prior art, the harvested marine diatom culture solution after culturing has a large stock and high salt content, and the cost consumed for sewage treatment is relatively large, which is one of the major obstacles to the industrial cultivation of marine diatoms. Therefore, the present application aims to provide a relatively simple reuse treatment method that can reduce the treatment cost of marine diatom culture solution.

[0050] In the first typical implementation manner of the present application, a reuse treatment method for marine diatom culture solution is provided. The reuse treatment method includes: S1, flocculating and preliminarily filtering the marine diatom culture solution after the nth marine diatom culture and harvest treatment in sequence to obtain a first filtrate; S2, performing macromolecular substance degradation and separation treatment on the first filtrate in sequence to obtain a reuse culture solution; S3, using the reuse culture solution to perform the (n + 1)th marine diatom culture on the marine diatom strain; n is a natural number greater than or equal to 1.

[0051] In this application, marine diatoms include, but are not limited to, Phaeodactylum tricornutum, Thalassiosira weissflogii, Thalassiosira punctigera, Odontella aurita, Thalassiosira pseudonana, Skeletonema costatum, Pseudo-nitzschia, Chaetoceros curvisetus, Chaetoceros muelleri and other algal species. Preferably, the types of marine diatoms include: Odontella aurita or Phaeodactylum tricornutum.

[0052] By sequentially performing flocculation, primary filtration, macromolecule degradation, and separation on the harvested marine diatom culture solution, the reuse of the culture solution can be achieved, reducing the waste liquid discharge of culturing marine diatoms and further reducing the culturing cost, which has a significant positive impact on environmental protection.

[0053] In the above treatment method, flocculation is performed first and then primary filtration is carried out, which can precipitate and remove the residual algal cells and some metal carbonates (such as calcium carbonate, magnesium carbonate, etc.) in the culture solution, and then degrade the macromolecules including proteins, polysaccharides, lipids, etc. in the supernatant, and then separate and remove the degraded products (i.e., the substances that may have an inhibitory effect on subsequent culturing), so as to obtain a culture solution that can be reused.

[0054] In order to further recycle the marine diatom culture solution multiple times, the marine diatom culture solution can be subjected to multiple reuse treatments according to requirements. In a preferred embodiment, the reuse treatment method further includes: S4, repeating steps S1 - S3 for the marine diatom culture solution after the n + 1 - th marine diatom culture and harvest treatment. Preferably, the number of repetitions is not limited, and more preferably it is 3 - 4 times. Preferably, the macromolecules include proteins, polysaccharides, and lipids.

[0055] In order to further remove the impurities in the culture solution after the degradation of macromolecular substances more completely, in a preferred embodiment, in step S2, after separating the products after the degradation of macromolecular substances and before obtaining the reusable culture solution, the reuse treatment method further includes filtration treatment; preferably, the filtration treatment includes primary filtration and / or secondary filtration. The primary filtration is carried out using the following filters: PP cotton filter and / or backwash filter (such as U-ZC-XD type backwash filter (powder sintered filter element)). The PP cotton contained in the PP cotton filter here is a multi-layer stacked filter screen structure with a smaller filtration pore size, which has a better effect than a single-layer filter screen; the secondary filtration is carried out using the following filtration media: at least one of activated carbon, hollow fiber membrane and ceramic membrane; preferably, the pore size of the PP cotton filter is 0.1-0.2 μm; preferably, the particle size of the activated carbon is 10-20 mesh (converted to mm, that is, 0.85-2.00 mm), and the iodine adsorption value is 1100-1300 mg / g, which is mainly used to further remove small molecule substances and pigments during the reuse process of repeating steps S1-S3. In order to further remove the impurities in the culture solution, in a preferred embodiment, the culture solution filtered through the activated carbon medium can also be ultrafiltered through an ultrafiltration device to obtain a reusable culture solution.

[0056] It should be noted that filtering using a protein separator, a PP cotton filter and an activated carbon filter can more thoroughly remove the substances after macromolecular degradation and the substances that do not need to be degraded and may affect the subsequent culture. If the above filtering treatment is not carried out, the substances that inhibit the subsequent culture after macromolecular degradation will still be retained in large amounts in the treatment solution, which still has a great impact on the subsequent growth culture and makes the subsequent reuse culture effect poor.

[0057] In order to more completely remove the residual algal cells in the seawater diatom culture solution and avoid damaging the flocs in the culture solution due to excessive stirring, in a preferred embodiment, the flocculation includes: adding a flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment and stirring. The flocculant is selected from at least one of polyacrylamide, chitosan, ferric trichloride, polyaluminium chloride and polyferric sulfate; preferably, the flocculation includes: adding a primary flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment and carrying out primary stirring to obtain a primary stirring product; adding a secondary flocculant to the primary stirring product and carrying out secondary stirring to obtain a secondary stirring product; preferably, the primary flocculant is selected from at least one of polyacrylamide and chitosan; the secondary flocculant is selected from at least one of ferric trichloride, polyaluminium chloride and polyferric sulfate.

[0058] It should be emphasized that the re - treatment of traditional algal culture solution to be processed usually uses polyacrylamide or polyaluminum chloride, or a combination of the two (but the residue of polyaluminum chloride will affect the subsequent diatom products, possibly leading to excessive heavy metals). Preferably, the present application uses a combination of polyacrylamide and ferric chloride for flocculation treatment. The flocculation method of the present application can not only better remove the residual algal cells in the culture solution, but also, since ferric chloride is a component required in the seawater diatom culture medium, the residual ferric chloride will not affect the culture of seawater diatoms.

[0059] In order to carry out the flocculation reaction efficiently and without destroying the nutrients in the culture solution, in a preferred embodiment, the speed of the first stirring is 60 - 90 rpm; preferably, the speed of the second stirring is 60 - 90 rpm; preferably, the final concentration of the first flocculant is 1 - 5 ppm; preferably, the final concentration of the second flocculant is 5 - 15 ppm. Preferably, the flocculation further includes: carrying out a third stirring on the product of the second stirring; preferably, the time of the third stirring is 10 - 15 min. Preferably, the speed of the third stirring is 60 - 90 rpm.

[0060] In order to further remove the flocculated impurities more completely, primary filtration is carried out after flocculation. The above "primary filtration" has no special meaning, only for distinction from other "filtrations" in the text, and conventional filtration methods in the art can be used. Preferably, the pore size of the filtration medium is 0.2 - 5 μm. More preferably, a double - layer filter screen with different pore sizes is set for primary filtration. In a preferred embodiment, the primary filtration includes: introducing the culture solution to be primarily filtered into the double - layer micro - filter screen for primary filtration; wherein, the double - layer micro - filter screen includes a first micro - filter screen and a second micro - filter screen, and the pore size of the first micro - filter screen through which the solution first flows is larger than that of the second micro - filter screen through which the solution then flows; preferably, the pore size of the first micro - filter screen is 1 - 5 μm; preferably, the pore size of the second micro - filter screen is 0.2 - 0.5 μm; preferably, in the double - layer micro - filter screen, the areas of the first micro - filter screen and the second micro - filter screen are each independently 10 - 15 m 2 ; preferably, the vertical distance between the first micro - filter screen and the second micro - filter screen is 50 - 70 cm; preferably, the import flow rate of the culture solution to be primarily filtered is 30 - 45 m 3 / h. In a preferred embodiment, the import direction of the culture solution to be primarily filtered is from the short side of the micro - filtration tank, so that the culture solution flows through the long side to complete the primary filtration treatment.

[0061] To further efficiently remove impurities such as bacteria and viruses from the seawater diatom culture solution, the culture solution after primary filtration is subjected to macromolecular substance degradation, including disinfecting the culture solution to complete protein degradation. In a preferred embodiment, the macromolecular substance degradation includes: adding a disinfectant to the first filtrate and performing a fourth stirring; in addition, in addition to the method of adding a disinfectant, the macromolecular substance degradation can also be carried out by using an ozone generator or an ultraviolet generator. Preferably, the disinfectant is sodium hypochlorite and / or chlorine dioxide; preferably, the time of the fourth stirring is 30 - 45 min; preferably, the chlorine concentration in the culture solution after macromolecular substance degradation is 10 - 20 ppm.

[0062] To further remove the products of the above macromolecular substance degradation and other impurities more completely, it is best to control the filtration flow rates within a suitable range. In a preferred embodiment, the separation treatment is carried out in a protein separator, and the treatment flow rate of the protein separator is 15 - 25 m 3 / h; preferably, the flow rate of the first filtration is 30 - 45 m 3 / h.

[0063] The principle of the protein separator for material separation is to use the bubbles on the water surface to adsorb various particulate dirt and soluble organic substances mixed in the water. The protein separator includes an aeration device or a vortex pump, which can generate a large number of bubbles. A large number of bubbles adsorbed with dirt gather on the water surface to form foam, which is collected and removed by a specific container in the protein separator, so that the culture solution passing through the device is further purified. Therefore, although it is named a protein separator, in fact, it can remove not only the degradation products of proteins, but also the degradation products of other macromolecular substances.

[0064] To further improve the sterility of the reused culture solution after reuse treatment, in a preferred embodiment, S3 includes: disinfecting the reused culture solution to obtain a pretreatment solution, mixing the pretreatment solution with seawater diatom algal seeds, and then performing the (n + 1)-th seawater diatom culture; preferably, the chlorine concentration in the pretreated solution after disinfection > 6 ppm, more preferably 6 - 10 ppm.

[0065] In a preferred embodiment, S3 includes: mixing the reused culture solution with seawater diatom algal seeds, adding a seawater diatom culture medium, and then performing the (n + 1)-th seawater diatom culture; preferably, the volume ratio of the reused culture solution to the seawater diatom culture medium for mixing is (100 - 1000):1; preferably, the volume ratio of the reused culture solution to the seawater diatom algal seeds is (3 - 10):1.

[0066] In another preferred embodiment, after the pretreatment solution is mixed with the seawater diatom algal species and before the (n + 1)-th seawater diatom cultivation, S3 further includes: adding a seawater diatom culture medium to the mixed solution of the pretreatment solution and the seawater diatom algal species, and then performing the (n + 1)-th seawater diatom cultivation; preferably, the volume ratio of the pretreatment solution to the seawater diatom culture medium is (100 - 1000):1; preferably, the volume ratio of the pretreatment solution to the seawater diatom algal species is (3 - 10):1.

[0067] When it is necessary to inoculate seawater diatoms in the photobioreactor for a new round of production, preferably, after reducing the chlorine concentration in the disinfected pretreatment solution to below 0.05 ppm, it is introduced into the photobioreactor and mixed with the seawater diatom algal species to reduce the impact of chlorine on the new round of seawater diatom cultivation. In the present application, there is no limitation on the method for reducing the chlorine concentration in the disinfected pretreatment solution. For example, it can be through photodegradation, neutralization reaction, etc.

[0068] In the present application, the seawater diatom culture medium can be selected according to the cultivated algae. In one preferred embodiment, the seawater culture medium contains nitrogen element, phosphorus element, iron element, magnesium element, zinc element, silicon element, vitamin B1, biotin, and vitamin B 12 .

[0069] In one preferred embodiment, the seawater diatom culture medium includes: 0.5 - 1.5 g / L NaNO3, 0.01 - 0.0315 g / L FeCl3·6H2O, 0.5×10 -4 -1.781×10 -4 . g / L MnCl2·4H2O, 0.5×10 -5 -2.3×10 -5 g / L ZnSO4·4H2O, 0.1×10 -5 -1.19×10 -5 . g / L CoCl2·6H2O, 0.5×10 -6 -2.5×10 -6 g / L CuSO4·5H2O, 0.2×10 -6 -1.84×10 -6 . g / L Na3VO4, 0.1 - 0.3 g / L NaSiO3·4H2O, 0.01 - 0.03 g / L NaH2PO4·H2O, 0.5×10 -4 -2×10 -4 μg / L vitamin B1, 0.1×10 -6 -1×10 -6 μg / L biotin, 0.1×10 -6 -1×10 -6 μg / L vitamin B12 。

[0070] The seawater diatom medium in the volume ratio of the recycled culture solution (or pretreatment solution) and the seawater diatom medium described above is the medium with the above components at normal concentrations. When applied in a smaller system, such as a system of about 1 L in the laboratory, the added seawater diatom medium is a concentrated medium, and the concentrated medium needs to be diluted. After each component reaches the normal concentration, the mixture is carried out in the above volume ratio.

[0071] In a preferred embodiment, the recycling treatment method further includes: when n > 5, evaporating and crystallizing the recycled culture solution to obtain distilled water and crystalline salts.

[0072] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0073] For those not specified in the embodiments regarding specific technologies or conditions, they are all conventional methods or are carried out according to the technologies or conditions described in the literature in this field, or according to the product instructions. For those reagents and instruments not specified in the manufacturer, they are all conventional products that can be obtained through regular channels. The instruments used in the embodiments of the present application are shown in Table 1 below:

[0074] Table 1:

[0075]

[0076] The specific method for culturing seawater diatoms is as follows:

[0077] In a laboratory system (i.e., an 800 mL system), in a glass columnar photobioreactor with a diameter of 6 cm, indoor culture of seawater diatoms (such as Phaeodactylum tricornutum or Odontella aurita) is carried out. The amount of seawater diatom medium used is 500 mL, the culture temperature is 22 - 25 °C, and the culture duration is 14 days; the culture light is 2500 - 10000 lux (equivalent to 50 - 200 μmol·m -2 ·S -1 ), and the change of algal dry weight with culture time is detected. The specific method is as follows: Take a certain volume of algal liquid, remove the supernatant by centrifugation, then dry the algal mud in the centrifuge tube, and subtract the weight of the centrifuge tube (previously dried to a constant weight) to obtain the dry weight of Odontella aurita; the change of fucoxanthin content with culture time is detected by ultraviolet spectrophotometry.

[0078] The composition of the seawater diatom medium is specifically as follows:

[0079] 1.5 g / L NaNO3, 0.0315 g / L FeCl3·6H2O, 1.781×10-4 g / L of MnCl2·4H2O, 2.3×10 - 5 g / L of ZnSO4·4H2O, 1.19×10 -5 g / L of CoCl2·6H2O, 2.5×10 -6 g / L of CuSO4·5H2O, 1.84×10 -6 g / L of Na3VO4, 0.3 g / L of NaSiO3·4H2O, 0.03 g / L of NaH2PO4·H2O, 2×10 -4 μg / L of vitamin B1, 1×10 -6 μg / L of biotin, 1×10 -6 μg / L of vitamin B 12 。

[0080] Control group

[0081] Directly use the seawater diatom medium to culture seawater diatoms. The seawater diatoms for culture are Odontella aurita and Phaeodactylum tricornutum respectively. Detect the algal dry weight and fucoxanthin content during the culture period. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product after the culture ends) and Figure 2-3 as shown. The fucoxanthin content here is the ratio of the fucoxanthin mass to the algal dry weight.

[0082] Example 1 (the specific process is as Figure 1 shown)

[0083] The seawater diatom for culture in this example is Odontella aurita.

[0084] S1, The seawater diatom culture solution (supernatant) after seawater diatom culture and harvest treatment is introduced into the flocculation tank through a water pump. Then, while using a peristaltic pump to add polyacrylamide (the final concentration of polyacrylamide is 1 ppm) to the seawater diatom culture solution, perform the first stirring to obtain the first stirring product. The speed of the first stirring is 60 rpm. Then, while using a peristaltic pump to add ferric chloride (the final concentration of ferric chloride is 5 ppm) to the first stirring product, perform the second stirring to obtain the second stirring product. The speed of the second stirring is 60 rpm. Perform the third stirring on the second stirring product. The time of the third stirring is 10 min. After completion, introduce the flocculated culture solution into the microfiltration tank for subsequent treatment;

[0085] Introduce the flocculated culture solution into the double-layer microfiltration mesh of the microfiltration tank through a needle brush pump. The flow rate of the needle brush pump is 30 m 3 / h. The flocculated culture solution is introduced from above the microfiltration mesh, and the direction is from the short side to the long side, flowing through the first microfiltration mesh and the second microfiltration mesh in sequence to obtain the first filtrate. The area of the microfiltration mesh is 10 m 2, with a size of 2×5m, the pore size of the first microfilter is 1μm, the pore size of the second microfilter is 0.2μm, and the distance between the upper and lower two layers of filters is 50cm.

[0086] S2, Pump the first filtrate into the disinfection and degradation tank through a water pump for the degradation of macromolecular substances. While adding sodium hypochlorite, perform the fourth stirring. The time of the fourth stirring is 30min. The chlorine concentration in the culture solution after the degradation of macromolecular substances is 20ppm, and it is introduced into the protein separator through a needle brush pump.

[0087] Pump the culture solution after the degradation of macromolecular substances into the protein separator through a needle brush pump to remove the degradation products of macromolecular substances such as proteins. The flow rate of the protein separator is 15m 3 / h; Pump the culture solution processed by the protein separator into a PP cotton filter (with a pore size of 0.2μm) through a water pump. The flow rate of the PP cotton filter is 30m 3 / h, and then introduce it into an activated carbon filter for filtration to obtain the recycled culture solution. The activated carbon particle size is 20 mesh, and the iodine adsorption value is 1100mg / g.

[0088] S3, Introduce the recycled culture solution into the storage tank for disinfection. Add sodium hypochlorite to the storage tank to obtain the pretreatment solution. The chlorine concentration in the pretreated solution after disinfection is 6ppm. When seawater diatoms need to be inoculated in the photobioreactor for a new round of production, use the method of photodegradation to reduce the chlorine concentration in the pretreatment solution to below 0.05ppm, and then introduce it into the photobioreactor. After adding the seawater diatom strain, mix it with the seawater diatom culture medium for subsequent seawater diatom culture and harvesting. Among them, the volume ratio of the pretreatment solution to the seawater diatom culture medium for mixing is 1000:1. The volume ratio of the pretreatment solution to the seawater diatom strain is 3:1.

[0089] Detect the algal dry weight and fucoxanthin content during the first use of the pretreatment solution for a new round of seawater diatom culture. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 2-3 as shown.

[0090] Example 2

[0091] Except that the operation of S3 is different from that in Example 1, the rest of the operations are the same as those in Example 1. The operation of S3 in this example is specifically as follows:

[0092] S3. Disinfect the storage pool into which the recycled culture solution is introduced. Add sodium hypochlorite to the storage pool to obtain a pretreatment solution. The chlorine concentration of the disinfected pretreatment solution is 6 ppm. When it is necessary to inoculate marine diatoms in the photobioreactor for a new round of production, use the method of photodegradation to reduce the chlorine concentration in the pretreatment solution to below 0.05 ppm, and then introduce it into the photobioreactor (without mixing with the marine diatom culture medium). Only use the pretreatment solution for subsequent cultivation and harvesting of marine diatoms. The volume ratio of the pretreatment solution to the marine diatom strain is 3:1.

[0093] Detect the algal dry weight and fucoxanthin content during the first use of the pretreatment solution for a new round of marine diatom cultivation. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of cultivation) and Figure 2-3 as follows.

[0094] Example 3

[0095] Except that the operation of S3 is different from that in Example 1, the rest of the operations are the same as those in Example 1. The operation of S3 in this example is specifically as follows:

[0096] S3. Disinfect the storage pool into which the recycled culture solution is introduced. Add sodium hypochlorite to the storage pool to obtain a pretreatment solution. The chlorine concentration of the disinfected pretreatment solution is 6 ppm. When it is necessary to inoculate marine diatoms in the photobioreactor for a new round of production, use the method of photodegradation to reduce the chlorine concentration in the pretreatment solution to below 0.05 ppm, and then introduce it into the photobioreactor. After inoculating the marine diatom strain, mix it with the culture medium containing only nitrogen and silicon salts, and carry out subsequent cultivation and harvesting of marine diatoms. The volume ratio of the pretreatment solution to the culture medium containing only nitrogen and silicon salts for mixing is 1000:1. The volume ratio of the pretreatment solution to the marine diatom strain is 3:1.

[0097] Among them, the composition of the culture medium containing only nitrogen and silicon salts is as follows:

[0098] 1.5 g / L NaNO3, 35 g / L sea salt, 0.3 g / L NaSiO3·4H2O, 2×10 -4 μg / L vitamin B1, 1×10 -6 μg / L biotin, 1×10 -6 μg / L vitamin B 12 .

[0099] Detect the algal dry weight and fucoxanthin content during the first use of the pretreatment solution for a new round of marine diatom cultivation. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of cultivation) and Figure 2-3 as follows.

[0100] Comparative Example 1

[0101] In this comparative example, except for the absence of the operations of primary filtration and macromolecule degradation, the remaining operations are the same as those in Example 1.

[0102] The algal dry weight and fucoxanthin content were detected when a new round of seawater diatom culture was carried out using the pretreatment solution for the first time. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 4-5 as shown.

[0103] Comparative Example 2

[0104] In this comparative example, except for the absence of the operations of primary filtration, macromolecule degradation and filtration using a protein separator, the remaining operations are the same as those in Example 1.

[0105] The algal dry weight and fucoxanthin content were detected when a new round of seawater diatom culture was carried out using the pretreatment solution for the first time. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 4-5 as shown.

[0106] Example 4

[0107] Except that the operation of S2 is different from that in Example 1, the remaining operations are the same as those in Example 1. The operation of S2 in this example is specifically as follows:

[0108] S2: The first filtrate is introduced into a disinfection and degradation pool through a water pump for macromolecule degradation. While adding sodium hypochlorite, the fourth stirring is carried out. The time of the fourth stirring is 30 min, and the chlorine concentration in the disinfected culture solution is 10 - 20 ppm, and it is introduced into a protein separator through a needle brush pump.

[0109] The culture solution after macromolecule degradation is introduced into a protein separator through a needle brush pump to remove the degradation products of macromolecules such as proteins therein. The flow rate of the protein separator is 15 m 3 / h; The culture solution processed by the protein separator is introduced into a PP cotton filter (pore size: 0.2 μm) through a water pump. The flow rate of the PP cotton filter is 30 m 3 / h, and then introduced into an activated carbon filter for filtration. The activated carbon particle size is 20 mesh, and the iodine adsorption value is 1100 mg / g;

[0110] The culture solution filtered by the activated carbon filter is introduced into an ultrafiltration device for further filtration. The pore size in the ultrafiltration device is 0.01 μm to obtain a reusable culture solution.

[0111] The algal dry weight and fucoxanthin content were detected when a new round of seawater diatom culture was carried out using the pretreatment solution for the first time. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 6-7 as shown.

[0112] Comparative Example 3

[0113] In this comparative example, except for the lack of the operation of degrading macromolecular substances, the remaining operations are the same as those in Example 1.

[0114] The algal dry weight and fucoxanthin content during the first new round of seawater diatom culture using the pretreatment solution were detected, and the results are shown in Table 2 (the algal dry weight and fucoxanthin content in the end product after the culture ended) and Figure 8-9 as shown.

[0115] Example 5

[0116] In this example, the cultured organism is *Phaeodactylum tricornutum*.

[0117] S1. The seawater diatom culture solution (supernatant) after seawater diatom culture and harvest treatment is introduced into the flocculation tank by a water pump. Then, while adding polyacrylamide (the final concentration of polyacrylamide is 1 ppm) to the seawater diatom culture solution by a peristaltic pump, the first stirring is carried out to obtain a first stirred product. The speed of the first stirring is 60 rpm. Then, while adding ferric chloride (the final concentration of ferric chloride is 5 ppm) to the first stirred product by a peristaltic pump, the second stirring is carried out to obtain a second stirred product. The speed of the second stirring is 60 rpm. The third stirring is carried out on the second stirred product, and the time of the third stirring is 10 min. After the end, the flocculated culture solution is introduced into the microfiltration tank for subsequent treatment;

[0118] The flocculated culture solution is introduced into the double-layer microfiltration mesh of the microfiltration tank by a needle brush pump. The flow rate of the needle brush pump is 15 m 3 / h. The flocculated culture solution is introduced from above the microfiltration mesh, and the direction is from the short side to the long side, flowing through the first microfiltration mesh and the second microfiltration mesh in sequence to obtain a first filtrate. The area of each microfiltration mesh is 10 m 2 , the size is 2×5 m, the pore size of the first microfiltration mesh is 1 μm, the pore size of the second microfiltration mesh is 0.5 μm, and the distance between the upper and lower two layers of meshes is 50 cm.

[0119] S2. The first filtrate is introduced into the disinfection and degradation tank by a water pump for macromolecular substance degradation. While adding sodium hypochlorite, the fourth stirring is carried out, and the time of the fourth stirring is 15 min. The chlorine concentration in the culture solution after macromolecular substance degradation is 20 ppm, and it is introduced into the protein separator by a needle brush pump.

[0120] The culture solution after macromolecular substance degradation is introduced into the protein separator by a needle brush pump to remove the degradation products of macromolecular substances such as proteins in it. The flow rate of the protein separator is 15 m 3 / h; The culture solution treated by the protein separator is introduced into a PP cotton filter (pore size 0.2 μm) through a water pump. The flow rate of the PP cotton filter is 30 m 3 / h, and then introduced into an activated carbon filter for filtration to obtain a reused culture solution. The activated carbon has a particle size of 10 - 20 mesh and an iodine adsorption value of 1100 mg / g.

[0121] S3. Disinfect the reused culture solution in the storage tank, add sodium hypochlorite to the storage tank to obtain a pretreatment solution. The chlorine concentration in the disinfected pretreatment solution is 6 ppm. When seawater diatoms need to be inoculated in the photobioreactor for a new round of production, the chlorine concentration in the pretreatment solution is reduced to less than 0.05 ppm by photodegradation and then introduced into the photobioreactor. The seawater diatom strain is inoculated and mixed with the seawater diatom culture medium for subsequent seawater diatom culture and harvesting. The volume ratio of the pretreatment solution to the seawater diatom culture medium is 1000:1. The volume ratio of the pretreatment solution to the seawater diatom strain is 3:1.

[0122] Detect the algal dry weight and fucoxanthin content during the first new round of seawater diatom culture using the pretreatment solution. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 10-11 as follows.

[0123] Comparative Example 4

[0124] In this comparative example, except for lacking flocculation, filtration using a protein separator, a PP cotton filter, and an activated carbon filter, and step S3, the remaining operations are the same as those in Example 1. The culture solution obtained after macromolecular substance degradation is introduced into the photobioreactor, and only the culture solution obtained after macromolecular substance degradation is used for subsequent seawater diatom culture and harvesting.

[0125] Detect the algal dry weight and fucoxanthin content during the first new round of seawater diatom culture using the culture solution obtained after macromolecular substance degradation. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 12-13 as follows.

[0126] Comparative Example 5

[0127] In this comparative example, except for lacking step S1, the remaining operations are the same as those in Example 1.

[0128] Detect the algal dry weight and fucoxanthin content during the first new round of seawater diatom culture using the pretreatment solution. The results are shown in Table 2 (the algal dry weight and fucoxanthin content in the final product at the end of the culture) and Figure 14-15 as follows.

[0129] Example 6

[0130] In this embodiment, except for the operation of filtering using a PP cotton filter being missing, the remaining operations are the same as those in Embodiment 1.

[0131] The algal dry weight and fucoxanthin content during the first new round of seawater diatom cultivation using the pretreatment liquid were detected, and the results are shown in Table 2 (the algal dry weight and fucoxanthin content in the end product after cultivation) and Figure 16-17 as shown.

[0132] Embodiment 7

[0133] In this embodiment, except for the operation of filtering using an activated carbon filter being missing, the remaining operations are the same as those in Embodiment 1.

[0134] The algal dry weight and fucoxanthin content during the first new round of seawater diatom cultivation using the pretreatment liquid were detected, and the results are shown in Table 2 (the algal dry weight and fucoxanthin content in the end product after cultivation) and Figure 16-17 as shown.

[0135] Table 2:

[0136]

[0137]

[0138] As can be seen from Table 2, the dry weight of Odontella aurita or Phaeodactylum tricornutum obtained from the reuse cultivation by one-time reuse treatment in Embodiments 1, 4, and 5, and the fucoxanthin content produced per unit of algae are close to the dry weight and fucoxanthin content obtained from normal seawater diatom cultivation once, indicating that the pretreatment liquid obtained by using the reuse treatment method of the present application can be used for normal cultivation of Odontella aurita and Phaeodactylum tricornutum, and the obtained cultivation results are better. In Comparative Example 1, primary filtration and macromolecule degradation treatment are missing; in Comparative Example 2, primary filtration, macromolecule degradation treatment, and treatment using a protein separator are missing; in Comparative Example 3, macromolecule degradation treatment is missing; in Comparative Example 4, flocculation, treatment using a protein separator, PP cotton filter, and activated carbon filter, and step S3 are missing; in Comparative Example 5, flocculation and primary filtration steps are missing. From the comparison of the algal dry weight and the fucoxanthin content produced per unit of algae with the control group, it can be seen that the results of the secondary cultivation using the pretreatment liquid lacking the above operations are all poor and cannot reach the effect of normal cultivation results.

[0139] Embodiment 8

[0140] Steps S1 - S3 of this embodiment are the same as those of Embodiment 1 and include S4, that is, steps S1 - S3 are repeated for the seawater diatom culture solution (supernatant after harvest) obtained by a new round of culture using the pretreatment solution, and the algal dry weight and fucoxanthin content during each new round of culture are detected. The culture effects of 1, 2, 3, 4, 5, and 6 new rounds of culture using the pretreatment solution are respectively detected, as Figure 18-19 shown.

[0141] It can be seen that during the first 5 cycles of culture, the biomass and fucoxanthin accumulation of Odontella aurita are close to those of the control group. When the 6th cycle of culture is carried out, the biomass and fucoxanthin accumulation of Odontella aurita begin to show a downward trend. It can be seen that when considering the ratio of input cost to benefit, steps S1 - S3 in the reuse treatment method of this application can be recycled at least 5 times, which can reduce the sewage discharge during large-scale production by more than 80%.

[0142] After the 6th S2 treatment, the reused culture solution can be introduced into a multiple-effect combined evaporator for evaporation crystallization. The distilled water returns to the fresh water storage tank, and the crystal salts are recovered for subsequent preparation of the seawater diatom culture medium.

[0143] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: By flocculating, initially filtering, degrading and separating macromolecular substances from the harvested seawater diatom culture solution, the reuse of the culture solution can be effectively realized, the waste liquid discharge of cultivating seawater diatoms is reduced by more than 80%, which has a significant positive impact on environmental protection and further reduces the culture cost. In addition, the reuse culture method of this application is simple to operate and has high treatment efficiency, and is more suitable for the recycling of the culture solution during large-scale seawater diatom culture, which plays an important role in improving the economic and ecological benefits of diatom culture.

[0144] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for reusing and treating a seawater diatom culture solution, characterized in that, The reuse treatment method includes: S1. Sequentially subjecting the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment to flocculation and primary filtration to obtain a first filtrate; S2. Sequentially subjecting the first filtrate to macromolecule degradation and separation treatment to obtain a reusable culture solution; S3. Using the reusable culture solution to perform the (n + 1)th seawater diatom culture on the seawater diatom strain; The n is a natural number greater than or equal to 1.

2. The reuse processing method according to claim 1, wherein The reuse treatment method further includes: S4. Repeating steps S1 - S3 for the seawater diatom culture solution after the (n + 1)th seawater diatom culture and harvest treatment; Preferably, the macromolecules include proteins, polysaccharides, and lipids.

3. The reuse processing method according to claim 1, wherein In S2, after separating the products after macromolecule degradation and before obtaining the reusable culture solution, the reuse treatment method further includes a filtration treatment; Preferably, the filtration treatment includes first filtration and / or second filtration. The first filtration is performed using the following filters: PP cotton filter and / or backwash filter; the second filtration is performed using the following filter media: at least one of activated carbon, hollow fiber membrane, and ceramic membrane; Preferably, the pore size of the PP cotton filter is 0.1 - 0.2 μm; Preferably, the particle size of the activated carbon is 10 - 20 mesh, and the iodine adsorption value is 1100 - 1300 mg / g.

4. The reuse processing method according to claim 1, characterized in that, The flocculation includes: Adding a flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment and stirring. The flocculant is selected from at least one of polyacrylamide, chitosan, ferric trichloride, polyaluminum chloride, and polyferric sulfate; Preferably, the flocculation includes: adding a first flocculant to the seawater diatom culture solution after the nth seawater diatom culture and harvest treatment and performing a first stirring to obtain a first stirring product; adding a second flocculant to the first stirring product and performing a second stirring to obtain a second stirring product; Preferably, the first flocculant is selected from at least one of polyacrylamide and chitosan; the second flocculant is selected from at least one of ferric trichloride, polyaluminum chloride, and polyferric sulfate.

5. The reuse treatment method according to claim 4, wherein The speed of the first stirring is 60 - 90 rpm; Preferably, the speed of the second stirring is 60 - 90 rpm; Preferably, the final concentration of the first flocculant is 1 - 5 ppm; Preferably, the final concentration of the second flocculant is 5 - 15 ppm.

6. The reuse processing method according to claim 1, characterized in that The primary filtration includes: Introducing the culture solution to be primarily filtered into a double - layer micro - filter screen for the primary filtration; Among them, the double - layer micro - filter screen includes a first micro - filter screen and a second micro - filter screen. The pore size of the first micro - filter screen through which the solution first flows is larger than that of the second micro - filter screen through which the solution then flows; Preferably, the pore size of the first micro - filter screen is 1 - 5 μm; Preferably, the pore size of the second micro - filter screen is 0.2 - 0.5 μm; Preferably, the introduction flow rate of the culture solution to be initially filtered is 30-45m 3 / h.

7. The reuse processing method according to claim 1, wherein The macromolecule degradation includes: adding a disinfectant to the first filtrate and performing a fourth stirring; Preferably, the disinfectant is sodium hypochlorite and / or chlorine dioxide; Preferably, the time of the fourth stirring is 30 - 45 min; Preferably, the chlorine concentration in the culture solution after degradation by macromolecular substances is 10-20 ppm.

8. The reuse processing method according to claim 3, characterized in that, The separation treatment is carried out in a protein separator, and the treatment flow rate of the protein separator is 15 - 25 m 3 / h; Preferably, the flow rate for performing the first filtration is 30 - 45 m 3 / h.

9. The reuse treatment method according to claim 1, wherein The S3 includes: Disinfecting the reused culture solution to obtain a pretreatment solution, mixing the pretreatment solution with a seawater diatom strain, and performing the (n + 1)-th seawater diatom culture.

10. The reuse processing method according to claim 1, wherein, The S3 includes: Adding a seawater diatom culture medium to the mixture of the reused culture solution and the seawater diatom strain, and performing the (n + 1)-th seawater diatom culture; Preferably, the volume ratio of the reused culture solution to the seawater diatom culture medium for mixing is (100-1000):1; Preferably, the volume ratio of the reused culture solution to the seawater diatom strain is (3-10):

1.

11. The reuse processing method according to claim 9, wherein After mixing the pretreatment solution with the seawater diatom strain and before performing the (n + 1)-th seawater diatom culture, the S3 further includes: Adding a seawater diatom culture medium to the mixture of the pretreatment solution and the seawater diatom strain, and then performing the (n + 1)-th seawater diatom culture; Preferably, the volume ratio of the pretreatment solution to the seawater diatom culture medium is (100-1000):1; Preferably, the volume ratio of the pretreatment solution to the seawater diatom strain is (3-10):

1.

12. The reuse processing method according to claim 10 or 11, characterized in that, The seawater diatom culture medium contains nitrogen element, phosphorus element, iron element, magnesium element, zinc element, silicon element, vitamin B1, biotin and vitamin B 12 ; Preferably, the seawater diatom culture medium comprises: 0.5 - 1.5 g / L of NaNO3, 0.01 - 0.0315 g / L of FeCl3·6H2O, 0.5×10 -4 -1.781×10 -4 . g / L of MnCl2·4H2O, 0.5×10 -5 -2.3×10 -5 g / L of ZnSO4·4H2O, 0.1×10 -5 -1.19×10 -5 . g / L of CoCl2·6H2O, 0.5×10 -6 -2.5×10 -6 g / L of CuSO4·5H2O, 0.2×10 -6 -1.84×10 -6 . g / L of Na3VO4, 0.1 - 0.3 g / L of NaSiO3·4H2O, 0.01 - 0.03 g / L of NaH2PO4·H2O, 0.5×10 -4 -2×10 -4 μg / L of vitamin B1, 0.1×10 -6 -1×10 -6 μg / L of biotin, 0.1×10 -6 -1×10 -6 μg / L of vitamin B 12 .

13. The reuse processing method according to claim 1, wherein The reuse treatment method further includes: When n > 5, evaporating and crystallizing the reused culture solution to obtain distilled water and crystal salts.

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